Semiconductor materials have been widely used to construct detector arrays for detecting radiation energy in imaging applications. One common implementation of a semiconductor detector array is a monolithic configuration in which both the radiation-sensitive material and signal-transmitting paths are formed on the same layer. Monolithic arrays are easy to manufacture and relatively inexpensive. However, the areas taken by the signal-transmitting paths do not directly sense radiation. This can reduce the image resolution and detection sensitivity.
A semiconductor detector array can also be formed in a hybrid configuration having a first radiation-sensitive layer and a separate second layer for signal transmission and processing. The two layers are often bonded together by bump bonds so that electrical signals can be transferred from the radiation-sensitive layer to the second layer. Since almost all area on the radiation-sensitive layer is used for sensing an input image, a higher fill factor can be achieved to improve the detection sensitivity and image resolution.
Two commonly used spectral ranges for many imaging applications are the infrared wavelengths and visible wavelengths. Different semiconductor materials are usually used in these two different spectral ranges since different energy band structures are needed to interact with the radiation.
Many conventional imaging systems or cameras are designed with semiconductor sensors to detect radiation in only one of these two common spectral ranges. Two different conventional imaging devices or cameras are often needed in order to detect images in both visible and infrared wavelengths.
In particular, certain applications require capturing images in both visible and infrared spectral ranges. For example, an object under measurement may produce both visible and infrared rays at the same time and both types of rays are needed to obtain useful information. However, using two different imaging devices for respectively detecting infrared and visible signals can be problematic in situations where space and weight for imaging equipment are limited. In addition, using two separate imaging devices is often more expensive than using a single imaging device.
It may be possible to perform imaging detection in both infrared range and visible range by using two separate detector arrays. The optical path in such systems can be split into an infrared path for the infrared detector array and a visible path for the visible detector array.